The invention relates to a welding device that is configured for sealing welding of thermoplastic hoses and that comprises a pinching device with at least two pinching jaws, of which at least one is movable and between which a hose, which is to be welded, can be pinched, wherein the pinching device has a heating device, which is coupled to a control unit and is configured to heat the hose pinched between the pinching jaws.
Furthermore, the invention relates to an automated metering device for the metered transfer of a medium from a supply container via a connecting hose, which is made of a thermoplastic material, into a target container, wherein the connecting hose can be positioned between at least two pinching jaws of a controllable pinch valve, which is coupled to a control unit, so that a volumetric flow rate of the medium can be controlled by controlling a pinching pressure that is exerted on the connecting hose by the pinch valve at a pinching point.
Finally the invention relates to the use of the aforementioned welding device in conjunction with the aforementioned metering device.
A welding device of the type described is known from the EP 0551813 B1. A metering device as described above is known from the EP 1525138 B1.
There is a strong trend in modern medical and biotech industries away from re-usable containers to single use containers, so-called “disposables.” As a rule, all manufacturing, dispensing, storage and application processes of medical and/or biotechnology fluids have to be carried out under aseptic conditions. In the event that re-usable containers are used, this requirement is fulfilled by first sterilizing the fluids and then checking and documenting the achieved sterility. The processes associated with this sequence of steps are technically intricate and cost intensive. They can be largely dispensed with if single use containers, i.e. disposables, which are already delivered in an aseptic condition by the manufacturer, are used. Plastic bags in particular have achieved success on the market as single use containers. They can be manufactured at a low cost, are easy to sterilize, are light in weight and have very little volume in the empty state, making them easy to dispose.
For typical processes both during the manufacture and also the use of medical and/or biotechnology fluids, the metering operations play an important role. These metering operations take place under various circumstances, e.g. during administration of the fluid, during mixing of various fluids or during dispensing of a fluid into commercially available containers. In any case at least one fluid has to be transferred from at least one supply container into at least one target container. Flexible plastic hoses are widely accepted for the purpose of connecting the supply container and target container, each of which is made as a plastic bag. Under hygienic aspects the coupling of the hose to a container is viewed critically, for which reason the manufacturers usually provide the bags as a single part or by material bonding with the hoses or with whole hose systems. Once the bag is filled, these hoses are permanently closed, typically at their ends, by welding. Closing the hoses by welding has many advantages. First of all, a bag, or more specifically a hose that is closed by welding, is tamper proof. Secondly, the end of the hose is heated by the welding operation, so that an additional sterilization process is carried out at the critical opening point. In principle, the welding operation is possible with any thermoplastic material, such as PVC, PE, PET, PU, etc.
The aforementioned EP 0 551 813 B1 discloses a welding device, in which the hose that is to be welded is pinched between two pinching jaws that are constructed as welding electrodes. The pinching pressure that is constant during the entire process is so high that it completely closes the free lumen of the hose at the pinching point. The pinching jaws together form a capacitor of an electric high frequency oscillating circuit. When the oscillating circuit is actuated at a suitably high frequency, the molecular dipoles of the hose material pinched between the pinching jaws are set into oscillation and, in so doing, heat up the walls of the hose. The heat buildup causes the hose to melt, so that under the constant pinching pressure the pinching jaws squeeze the softened hose material out of the pinching point, so that the initial result is the welding followed by a severing of the welding point. This publication document focuses, in particular, on the tuning of the resonance frequency of the electric oscillating circuit, where this resonance frequency changes through the passive approach of the pinching jaws under the constant pinching pressure owing to the resulting capacitance change of the capacitor.
The aforementioned EP 1 525 138 B1 discloses a metering device, with which a plurality of small bags provided as the target containers can be filled from a large bag functioning as the supply container. The metering, i.e. the control of the volumetric flow rate from the supply container to the target containers, is performed using pinch valves, which pinch the hose connections between the supply container and the target containers between the actively controllable pinching jaws. In so doing, the pinching pressure is varied in a controlled manner, so that the free lumen of the respective hose at the pinching point changes, and the volume flow through the hose at the pinching point can be varied, as required. Following completion of the bag filling operation, the access hose of the respective target bag is closed with a lock clamp and, in addition, can be permanently welded, for example, with the aforementioned welding device. A drawback of this approach is that the welding of the access hoses for the target containers has to be performed in a separate working step, a feature that entails not only higher costs due to the amount of time that is required and the need for an additional welding device but also entails hygienic risks.